This invention relates to a microlensed optical fiber and a method of making the same. The microlensed optical fiber of the present invention is useful in a variety of optical systems including optical switches, connectors and terminals.
The development, miniaturization, and simplification of optical devices for applications such as computing and communications depends on the development of new optical components. Particularly desirable are optical coupling components that are easy and economical to fabricate, durable, and that have a high coupling efficiency.
Conventional coupling systems using a discrete spherical lenses, ball lenses, grin lenses (gradient refractive index) joined to the optical fibers via adhesives suffer because aligning the lens with the fiber is difficult. Fabrication is therefore expensive and often results in high variability among components. These components may also suffer from mechanical and thermal instability.
A microlensed fiber, having the lens and the fiber fused together as a single unit is a desirable alternative to adhesive-joined coupling systems. One method of fabricating such a component is to melt the tip portion of an optical fiber, to form a spherical lens connected to the fiber tip. This requires to a very uniform heat source to allow for the formation of highly uniform spherical lens surface (see for example U.S. Pat. No. 5,293,438 and references therein). Because the temperature that is required to form a spherical lens is higher than that required to simply splice two fibers together, more power must be supplied to the heat source. This results in increased wear, increased maintenance, and shorter lifetimes for the heating equipment. Accordingly, it is desirable to develop a method of fabricating a microlensed fiber that requires less heating power and is therefor capable of producing many units between maintenance cycles.
One aspect of the present invention is to provide a microlensed fiber comprising a plano-convex refractive lens spliced to an optical fiber. According to one embodiment, the lens comprises silica doped with one or more compounds selected from X2O, YO, Z2O3, TO2, or R2O5; wherein
X is Na, K, Li, Al, or Cs;
Y is Mg, Co, or Zn;
Z is B, Al, Ga, Sb or Bi;
T is Ge or Ti; and
R is P.
A further aspect of the present invention is to provide a process for manufacturing a microlensed fiber comprising;
a) splicing a doped silica rod to an optical fiber by contacting an end of the optical fiber with an end of the doped silica rod and heating the area of contact to a temperature effective for joining the fiber and the rod,
b) heating a region of the doped silica rod while simultaneously applying tension to the rod such that the doped silica rod is cut in the heated region to a desired predetermined length, and
c) heating a region of the doped silica rod that remains spliced to the optical fiber so that the end of the doped silica rod melts into a plano-convex lens surface with a desired radius of curvature.